Artificial disc technology has been employed as a surgical approach to repair or replace damaged spinal discs in an attempt to relieve debilitating neck and back pain, and to maintain or restore intervertebral spacing while attempting to minimize their constraining effects on the normal biomechanical movement of the spine. The quest for a more physiologic device to accomplish these goals began in the 1950s and continues to this day.
Total disc replacement is still a relatively new, promising field of spine implant technology that has the potential to revolutionize the treatment of degenerative disc disease. It is clear from both short-term in-vitro and clinical data, that disc replacements can successfully preserve the motion of a treated spine and significantly reduce the potential incidence of adjacent level disc degeneration. But unfortunately, not unlike as many as 40% of spinal fusions performed worldwide, disc replacements may also need to be revised due to poor implantation technique, component wear, or failure of the device, to name but a few.
Clinical data has illustrated that many failures occur as a result of over-aggressive bone bed preparation or excessive protuberances on the implants both of which can result in compromise of the vertebral endplates. Other data suggests that many design failures resulted from point loading or inadequate load distribution across the endplate. Still other designs suffer from poor choices of materials for articular wear bearings, oxidation, and/or inadequate long-term wear characteristics between device sub-components. Each of the aforementioned deficiencies may ultimately result in subsidence, loss of designed function, or even spontaneous fusion.
It may be a generation before sufficient data emerges to clearly delineate the long-term successful designs from the catastrophic failures, but given that most of the currently pending or recently approved artificial disc implants in the market are based on design fundamentals utilized in other orthopedic applications that have already been demonstrated to fail for predictable reasons, one might expect to see many of these designs fail in similar fashion for the same reasons. Accordingly, there remains a need for better artificial disc technology that addresses these shortcomings by providing an artificial disc that does not significantly inhibit spinal movement, minimizes any potential for wear between disc components and or vertebral bodies, improves upon the surgical technique utilized to implant them, reduces the potential for histocytic foreign body and/or inflammatory response, and provides physiologic load bearing and joint spacing functions akin to the normal, healthy spinal disc. In addition, there also remains a need for better salvage and fusion devices to replace other failed artificial discs.